This invention refers to a grinding wheel and to a method of grinding bar blades, particularly carbide blades for the production of bevel and hypoid gears having arcuate teeth.
A known blade for the production of arcuate teeth is designed as a cuboid bar with a shaft having a trapezoidal end. The trapezoidal end comprises a relief flank, a minor flank, a head surface connecting the relief flank with the minor flank, and a rake flank.
A method and a grinding wheel for grinding carbide inserts affixed to the teeth of a grinding tool are known from EP 0 343 983 A2. The design of the grinding wheel is such that its working regions are capable of grinding not only flat surfaces on the carbide inserts, but also adjacent curved surfaces of the tooth.
It is the object of the present invention to provide a grinding wheel and a method for rapid, efficient and precise grinding of bar blades.
The grinding wheel according to the invention has a conical grinding surface smoothly adjoined by a cylindrical grinding surface smoothly adjoined in turn by a toroidal grinding surface. Therefore, the relief flank, the minor flank and the rake flank can be rough ground by profile grinding with the method according to the invention using the conical grinding surface and its area of transition to the cylindrical grinding surface. The relief flank and the minor flank can be subsequently finish ground by generating grinding at the toroidal grinding surface. In this manner it is possible with one single grinding wheel not only to rough grind all three essential surfaces, namely the relief flank, the minor flank and the rake flank, but also to finish grind the relief flank and the minor flank without resetting the blade. This permits performance of a rapid, complete and precise grinding of the blade.
In one advantageous embodiment of the invention the conical and the cylindrical grinding surfaces have a coarser grain than the toroidal grinding surface. For this reason, the minor flank and the relief flank can be rough ground and the rake flank can be ground, all at high stock removal rates.
In another advantageous embodiment of the invention, the cylindrical grinding surface merges tangentially into the toroidal grinding surface. For this reason it is advantageously possible in one translational movement first of all to rough grind the head surface of the blade with the cylindrical grinding surface, and to finish grind it with the adjacent toroidal grinding surface. This combination of rough grinding and finish grinding of the head surface in one operation reduces the amount of time required for the entire blade grinding process.
In yet another advantageous embodiment of the invention a first radius is formed between the conical grinding surface and the cylindrical grinding surface. The toroidal grinding surface here has a circular arcuate cross section with a second radius. The first radius here is larger than the second radius. During the roughing, i.e. in profile grinding of the blade, the relief flank or the minor flank or the rake flank of the blade is brought into contact with the conical grinding surface in such a manner that a respective shoulder surface is ground at the transition of the relief flank or the rake flank to the blade shaft by the first radius and the transition between the conical and the cylindrical grinding surface, or in addition by a portion of the cylindrical grinding surface. Following the profile grinding, the relief flanks or the rake flank is finished by generating grinding with an overlapping relative translational movement between the blade and the grinding wheel relative to the toroidal grinding surface. Since the radius of the toroidal grinding surface is smaller that the first radius in the transitional area between the conical grinding surface and the cylindrical grinding surface, the respective associated shoulder surface does not have to be ground along with the relief flank or the minor flank during their finishing. This means that the toroidal grinding surface is spared and therefore has a longer working life. Furthermore, the grinding process is abbreviated, since the shoulder surfaces between the relief flank or minor flank and the shaft do not have to be finish ground.